An Investigation of the Structure and High Temperature Mechanical Properties of Oxide Dispersion Strengthened Alloys.

Abstract

Abstract : The research work deals with the structure and mechanical properties of high temperature metals and alloys in which a significant contribution to strengthening is made by dispersed second phase particles. Because the research has been conducted on both aluminum and nickel based alloys, this report is organized along these lines. We have studied, for the first time, the combined effects of oxide dispersion and solute strengthening at high temperatures in an ODS aluminum-magnesium alloy. We find that the oxide particles contribute significantly to the strength at high temperatures, as expected, but that the strength of the ODS alloy at intermediate temperatures is actually lower than that for the solid solution without oxide particles. This suggests that solute strengthening cannot be combined efficiently with oxide strengthening in the design of ODS alloys. Because rapidly solidified aluminum alloys are so similar to ODS aluminum alloys, a study of the high temperature strength properties of Al-Fe-Ce alloys has alloys has also been conducted. We find these alloys to be much stronger than ODS aluminum at low and intermediate temperature but they are much weaker than the ODS alloys at very high temperatures. This weakening effect is caused mainly by twinning deformation of the intermetallic particles at high temperatures. This suggests that much more refractory particles, such as oxides or carbides, are needed for high temperature strength.